Indian Ocean tsunamis: environmental and socio-economic impacts in Langkawi, Malaysia     

MICHAEL BIRD  SUSAN COWIE  REA HAWKES†  BEN HORTON†  COLIN MACGREGOR  JIN EONG ONG‡  AILEEN TAN SHAU HWAI§  TEH TIONG SA¶  ZULFIGAR YASIN§ 《The Geographical journal》2007,173(2):103-117

We report the results of a study of the physical characteristics and socio-economic impacts of the Indian Ocean Tsunami of 26 December 2004 on the tourist island of Langkawi, Malaysia. In comparison with many other locations struck by the tsunami, the immediate physical and socio-economic impacts in Langkawi were relatively minor. A detailed survey of the watermark and ground elevations was undertaken in the worst affected area between Sungei Kuala Teriang and Sungei Kuala Melaka. Here, the tsunami reached a maximum elevation of 4.29 m as it crossed the coast, with a maximum flow depth of 2.0 m and a very consistent run-up elevation relative to mean sea level of 300 ± 10 cm. The tsunami inundated inshore areas for 300 m and penetrated inland along creeks for 500–1000 m. Structural damage to buildings was confined to within 50–150 m of the shoreline where about 10% of the houses were completely destroyed and 60–70% suffered significant structural damage. Damage was particularly severe in areas where there was no engineered coastal protection, but while coastal revetments did provide enhanced protection for houses at the waterfront, the coastline in the study area appeared to be more heavily impacted than elsewhere in Langkawi because wave energy was focused on the area by offshore breakwaters built to protect the Langkawi port and airport. Emergency response after the tsunami was rapid and efficient but would have been improved if the local police station had not been rendered inoperative by the first wave, and if a mechanism had been in place to ensure that informal advance warnings transmitted between Phuket (Thailand), Langkawi and Penang (Malaysia) by tourist operators could have been more widely disseminated.  相似文献   

Phase Equilibrium Constraints on Intensive Crystallization Parameters of the Ilimaussaq Complex, South Greenland   总被引：4，自引：1，他引：4  

MARKL  GREGOR; MARKS  MICHAEL; SCHWINN  GREGOR; SOMMER  HOLGER 《Journal of Petrology》2001,42(12):2231-2257

The 1·13 Ga Ilímaussaq intrusive complex, SouthGreenland, is composed of various types of alkali granite andsilica-undersaturated alkaline to agpaitic nepheline syenitesrelated to three subsequently intruded magma batches. Mineralchemistry indicates continuous fractionation trends within eachrock type, but with distinct differences among them. The last,peralkaline magma batch is the most fractionated in terms ofX_Fe^{mafic mineral}, feldspar composition and mineral assemblage.This indicates that an evolving magma chamber at depth discontinuouslyreleased more highly fractionated alkaline melts. Fluid inclusionsin some sodalites record a pressure drop from 3·5 to1 kbar indicating that crystallization started during magmaascent and continued in the high-level magma chamber. On thebasis of phase equilibria and preliminary fluid inclusion data,crystallization temperature drops from >1000°C (augitesyenite liquidus) to <500°C (lujavrite solidus) and silicaactivity decreases from  相似文献   

An Ion and Electron Microprobe Study of the Mineralogy of Enclaves and Host Syenites of the Red Hill Complex, New Hampshire, USA     

DORAIS  MICHAEL J.; FLOSS  CHRISTINE 《Journal of Petrology》1992,33(5):1193-1218

The Red Hill complex of New Hampshire is unusual for the WhiteMountain Magma Series of northern New England because it consistsof both silica-undersaturated and -saturated to -oversaturatedsyenites. Amphibole, pyroxene, and apatite in two of the saturatedunits, the Outer Coarse Syenite (OCS) and the Garland Peak Syenite(GPS), and in the undersaturated Nepheline Sodalite Syenite(NSS), were analyzed to determine the relationship between coexistingunder-saturated and saturated magmas. Mafic enclaves in theNSS and the GPS were also studied to elucidate their relationshipswith the host syenites. In addition to mafic enclaves, the NSS contains later emplacedcamptonitic dikes and associated pipe-like benmoreites. Thebenmoreites contain amphibole that is compositionally continuouswith amphibole in the NSS. However, REE and other trace elementabundances in apatite from the benmoreites and the NSS are notcompatible with a genetic relationship between the two. Maficenclaves within the NSS contain amphibole and pyroxene thatare compositionally continuous with the NSS. Bulk-rock compositionsof the enclaves plot along trends defined by the NSS. Furthermore,chondrite-normalized REE patterns for apatite in both the enclavesand the NSS are parallel, and REE abundances increase systematicallyfrom the enclaves to the NSS. We therefore suggest that theenclaves represent magmas similar to the NSS parent that intrudedup into its daughter products. These magmas appear to have beentephritic to phonotephritic in composition. Abundances of REE in apatite in the Nepheline Sodalite Syenite(NSS) are distinct from those in apatite in the silica-saturatedOCS. OCS apatites have LREE abundances up to 26 000 times chondritesand La/Yb ratios of 16–27. NSS apatites have comparableLREE concentrations, but HREE abundances are considerably lowerthan those of the OCS; La/Yb ratios range from 68 to 104. Theseobserved differences in both the REE and other trace elementabundances between apatite in the two rocks present difficultieswith a common parental magma hypothesis for the NSS and OCS.Hence it is suggested that, although the OCS and NSS are contemporaneousin time and space, they are probably not consanguineous. The silica-saturated GPS is a fine-grained syenite containingstrongly zoned amphiboles with kaersutite to hastingsite coresrimmed by hastingsitic hornblende and ferro-hornblende. Discretegrains of hastingsitic hornblende and ferro-hornblende occurin a feldspar-quartz groundmass. Coarser-grained, quartz-richpatches, containing feldspars and ferro-hornblende and ferroedenite,are also found in the GPS. The kaersutite cores are identicalto the amphibole in the GPS enclaves and the NSS suite. TheseGPS enclaves are silica undersaturated; the kaersutite coresin the GPS host rocks are probably xenocrysts derived from disaggregatedundersaturated magmas similar to that represented by the enclaves.  相似文献   

A new location of Holocene dolomite formation, Lake Hayward, Western Australia     

MICHAEL R. ROSEN  LEE COSHELL† 《Sedimentology》1992,39(1):161-166

Holocene dolomite forms in the sediment of Lake Hayward, a small permanent hypersaline lake in the Clifton-Preston Lakeland System, Western Australia. The geomorphological setting of dolomite formation in Lake Hayward is similar to the Coorong region in South Australia. Unlike in the Coorong region, dolomite in Lake Hayward does not form as a direct precipitate from the lake water, but is of diagenetic origin. This can be deduced from the following features: (1) the dolomite occurs only below 60–70 cm from the sediment-water interface, (2) dolomite occurs as luminescing cement, and (3) dolomite has pristine well-formed rhomb-shaped crystals. The source of magnesium for dolomitization is probably from the concentration on inflowing groundwater by evaporation and the selective removal of calcium by chemical and biological aragonite/calcite precipitation.  相似文献   

Fayalitic olivine in CV3 chondrite matrix and dark inclusions: A nebular origin     

MICHAEL K. WEISBERG  MARTIN PRINZ 《Meteoritics & planetary science》1998,33(5):1087-1099

Abstract— Fayalitic olivine (Fa₃₂) is the major component of the matrices and dark inclusions of CV3 and other unequilibrated chondrites. It occurs most commonly as rims, veins and halos in and around chondrule silicates in the Allende-type (CV3_OXA) chondrites and, to a much lesser extent, in the reduced (CV3R) and Bali-type (CV3OXB) chondrites. The olivines have distinctive platy, tabular and lath- or irregular-shaped crystals, with the ratio of the two types varying widely. In CV3_OXB chondrites, matrix fayalitic olivines range up to Fag_99.9; whereas, in the other CV3 chondrites, the range is much smaller. The platy and tabular anisotropic forms of the fayalitic olivines strongly suggest growth from a vapor, and the nature of the occurrences suggests that CV3 matrices are unequilibrated mixtures of nebular materials. We argue that the parent body hydration/dehydration model has numerous inconsistencies that make this hypothesis highly unlikely. These include: (1) There is no direct evidence linking fayalitic olivine to precursor phyllosilicates. (2) Dehydration of phyllosilicates cannot explain the wide range of morphologies of the fayalitic olivines. (3) Fayalitic olivine clearly predates the formation of the hydrous phases in CV3 chondrites and is one of the phases that breaks down to form phyllosilicates (Keller et al., 1994). (4) The unequilibrated nature of the matrix, including fine-scale zoning in 10 μm sized fayalitic olivine crystals, would not survive the parent body metamorphism required in the dehydration model. (5) A dark inclusion in the Ningqiang chondrite contains fayalitic olivine rimmed by glassy and microcrystalline material (Zolensky et al., 1997), which probably formed by radiation damage. This indicates that the fayalitic olivine was exposed to solar radiation in a nebular setting. (6) Some Allende chondrules contain unaltered primary, anhydrous glassy mesostasis in contact with the host matrix (e.g., Ikeda and Kimura, 1995). Chondrule mesostases would not have survived parent body hydration without becoming hydrated and would probably not survive the metamorphic heating required in the dehydration scenario. (7) Single platy and barrel-shaped crystals of fayalitic olivine are present in accretionary rims in calcium-aluminum-rich inclusions (CAIs) (MacPherson and Davis, 1997), which developed in the nebula. (8) Matrix lumps completely encased in chondrules in ordinary chondrites contain mainly fayalitic olivine (Scott et al., 1984), which indicates a nebular origin. (9) Oxygen isotopic compositions of Allende matrix and dark inclusions strongly indicate little or no hydration for Allende and its components (Clayton, 1997). We favor a nebular vaporization/recondensation model in which vaporization of chondritic dust produced a fayalite-rich vapor, followed by formation of the fayalitic olivine by direct recondensation from the vapor, epitactic growth on surfaces of existing forsterite and enstatite in chondrules, and replacement of existing forsterite and enstatite by gas-solid exchange.  相似文献   

MOPAN MAYA FOREST RESOURCES IN SOUTHERN BELIZE     

MICHAEL K. STEINBERG 《Geographical review》1998,88(1):131-137

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“THE END OF MODERN HISTORY”?*     

MICHAEL WILLIAMS 《Geographical review》1998,88(2):275-300

ABSTRACT. The first half of the twentieth century marked both an end to confidence in human control of the earth and a prelude to the contemporary era of intense environmental concern after 1950. This conspectus of the environmental history/historical geography of the transitional years between 1900 and 1950 focuses on rising concerns over resource supplies and exploitation, particularly land settlement, timber supplies, soil erosion, and river-basin control. Conservation and the pervasiveness of ecological thinking and analogy form a strong underlying theme.  相似文献   

Origin of well-rounded gravels in glacial deposits from Brøggerhalvøya, northwest Spitsbergen: potential problems caused by sediment reworking in the glacial environment     

DAVID HUDDART  MATTHEW R. BENNETT  MICHAEL J. HAMBREY  NEIL F. GLASSER  KEVIN CRAWFORD 《Polar research》1998,17(1):61-70

Well-rounded gravels are described from moraine-mound complexes, diamicton forefields and modern englacial thrusts at the margins of four glaciers on the northern side of Brøggerhalvøya, northwest Spitsbergen. Their shape charcteristics are compared with modern and fossil glacigenic, modern beach and Early Weichselian beach gravels from this peninsula. The best discriminators of the well-rounded gravels have been found to be the percentage-frequency roundness histograms, the roundness mid-point and roundness range diagrams and the sphericity-roundness plots. It is concluded that the gravels have been derived by englacial thrusting from Early Weichselian or last interglacial beaches in the inner parts of the fjord and in the low level cirques when sea level reached at least 50m a.s.l. and deposited the beach gravels. The discrimination between gravel in basal diamictons, proglacial outwash and modern beaches is difficult as the reworking has resulted in little particle shape change. The potential major problem caused by reworking in the glacial environment is emphasised. especially when clast shape comparisons from modern environments to older sediments are used.  相似文献   

Carbonate tidal rhythmites from the Middle Jurassic of Britain     

MICHAEL ASHTON 《Sedimentology》1981,28(5):689-698

Newly discovered carbonate laminites are described from the Lincolnshire Limestone Formation (Middle Jurassic, Britain). These occur in the upper peloidal unit of fining-upward rhythms which comprise much of the lagoonal lower Lincolnshire Limestone in south Lincolnshire. The flat, millimetre-scale laminations are of three types: (1) alternating peloid-rich, peloid-poor laminae; (2) alternating bioclastic and peloidal laminae; (3) alternating bioclastic and micritic laminae. In all three types, small-scale cross-laminated sets (usually < 40 mm thick) also occur. The laminite horizons are usually < 150 mm thick and have, in some cases, been traced laterally for ～100 m. The close analogy of these carbonate laminites with siliciclastic counterparts favours their interpretation as tidal rhythmites, mechanically deposited in a low intertidal/shallow subtidal setting. The associated sedimentary features and overall stratigraphic-sedimentologic position of the deposits support this conclusion. According to the literature, mechanically deposited as opposed to algally induced carbonate laminites are rare outside the supratidal realm. Possible reasons for the real or imagined scarcity of intertidal/ subtidal carbonate laminites in ancient sedimentary regimes are discussed.  相似文献   

A simulation model of alluvial stratigraphy   总被引：8，自引：0，他引：8  

JOHN S. BRIDGE  MICHAEL R. LEEDER 《Sedimentology》1979,26(5):617-644

The quantitative model presented simulates the development of a two-dimensional alluvial sedimentary succession beneath a floodplain traversed by a single major river. Several inter-related effects which influence the distribution of channel-belt sand and gravel bodies within overbank fines are accounted for. These are (a) laterally variable aggradation, (b) compaction of fine sediment, (c) tectonic movement at floodplain margins, and (d) channel avulsion. Selected experiments with the model show how the interconnectedness and areal density of channel-belt deposits decrease with increasing floodplain width/channel-belt size, mean avulsion period, and channel-belt aggradation rate. Separation of stream patterns based on interconnectedness and channel deposit density is difficult. Tectonic movements do not have a significant influence upon the successions unless a preferred direction of tilting is maintained (half-graben). Then channel-belt deposits showing offlap tendencies tend to cluster adjacent to the active floodplain margin, leaving dominantly fine-grained alluvium to accumulate on the inactive side. Individual channel-belt deposits thicken during aggradation, although a self-regulating limit to such thickening is likely to operate. ‘Multistorey’features resulting from aggradation may be difficult to tell apart from those arising through superposition of distinct channel-belt deposits of avulsive origin.  相似文献